Television audiences can’t seem to get enough of “Downton Abbey,” the British series that premiered in 2010 and in the U.S. the following year. But while the series is set in a fictional Yorkshire country estate, there is a real story in the British aristocracy that may be even more captivating than the TV series.

“Lady Catherine, the Earl, and the Real Downton Abbey” is the meticulously researched story of Catherine Wendell, the beautiful and spirited American woman who married Lady Almina’s son, the man who would become the 6th Earl of Carnarvon.

And the author of this book has a unique access to the historical material she needed to write it — she is the Countess of Carnarvon.